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The most common explanation of what would happen to a space-ship that falls into a black hole ends with spaghettification.

However imagine there was a space-ship built out of unobtanium, that could provide enough artificial gravity to counter-act the effects of the black hole on the ship's contents. As the ship is falling into the hole, gravity is increasing, which in turn slows down the relative passage of time. Eventually billions of years pass "on the outside" and the black hole evaporates through Hawking radiation, which reduces the event horizon and allows the ship to escape.

Could this scenario be used to allow a hypothetical astronaut to travel billions of years into the future in the duration of a regular human life?

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  • $\begingroup$ If the effects of falling into it can be counteracted then it is not a black hole, by definition. This is exactly the kind of premiss which contains its own negation. $\endgroup$ – AlexP Nov 30 '16 at 13:55
  • $\begingroup$ @AlexP couldn't a sufficiently strong material withstand being inside the event horizon? $\endgroup$ – JonathanReez Nov 30 '16 at 13:59
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    $\begingroup$ The event horizon is the place where the direction towards the black hole becomes timelike, that is, the direction towards the black hole becomes the future and the direction away from the black hole becomes the past. Locally the event horizon is nothing special; the only problem is that when an object is inside the event horizon it cannot escape, because the direction away from the black hole is in it's past. $\endgroup$ – AlexP Nov 30 '16 at 14:06
  • $\begingroup$ I think you might be able to avoid some of AlexP's arguments by rewording. "Falling into a black hole" typically means you passed the event horizon, which even Stephen Hawking considers to be a one way trip if you want to call yourself "human" on the way out. It sounds like you just want to get very near the event horizon. This is a more tractable problem because it lets our space-ship remain in a region of space-time that's much easier to work out the math on. However, you will need something like anti-gravity, and the implications of that are.. odd. $\endgroup$ – Cort Ammon Nov 30 '16 at 14:20
  • $\begingroup$ I'll give u the benefit of doubt and say everything goes according to ur plan, billions and billions of years later assuming the black hole do evaporate wouldn't that leaves nothing... $\endgroup$ – user6760 Nov 30 '16 at 14:21
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Here's the thing about spaghettification: there's nothing your ship can do to protect you.

The problem is that spaghettification is caused due to the fact that, near a strong gravitational force, the difference in distance between your feet and the gravitational source and the distance between your head and that gravitational source actually starts to matter. There's an r^2 term in gravitational forces. Your feet will feel a higher acceleration than your head will.

Which means the concept of free-fall breaks down. Your feet will constantly want to accelerate faster than your head will. It is this effect that tears your body to ribbons. It doesn't matter if the spaceship is made of adamantium or unobtanioum, because this effect passes right through it.

To do what you want, you need a source of anti-gravity that is tuned correctly to oppose this effect, or some anti-gravity shielding. Unfortunately, the closer you get to the black hole, the more anti-gravity you have to tune up. Anti-gravity doesn't exist, so science doesn't actually know what it would behave like, but it's reasonable to assume it would cancel out the relativistic gravitational effects as well, so the affected region would find time passes like normal. It probably wouldn't slow down like you want.

If you were try to push this to an extreme, passing through the event horizon, we'd have to sit down and really nail down the math you want for anti-gravity. We'd have to do it at the college physics/general relativity level, and it would be difficult. You'd have lots of infinities and infinitesimals creeping in which would take a lot of work to nail down. And, in the end, my conjecture would be that you'd still find time didn't slow down for you, even after that virtually infinite amount of effort.

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    $\begingroup$ Successfully calculating all of that sounds very improbable. I wonder if we could start by figuring out exactly how improbable it is? $\endgroup$ – Robert Columbia Nov 30 '16 at 14:56
  • $\begingroup$ I believe the question assumes that the ship can use antigravity, it is even made of unobtainium. Your answer assumes real life, but the question has already thrown that out the window. $\endgroup$ – Ryan Nov 30 '16 at 16:53

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